IllegalArgumentException in Java — What It Means and How to Fix It

What Java's IllegalArgumentException means and how to fix it.

Published November 2, 2026

IllegalArgumentException is thrown to indicate a method has been passed an argument that is inappropriate for it.

Key points

  • Read the full stack trace from the top — it names the exact class, method, and line where the exception originated

Example

A common exception to throw deliberately from your own methods when validating input parameters
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